Believe it or not, this soup was my favorite food as a kid. I would order it every time it appeared on a restaurant menu, and even loved the Cambell’s canned version at home. So, while my whole family was greatly in need of some comfort food this week, I brought back this old classic and it was a huge hit. I lightened it up a bit from the cream-and-butter-filled soups I remember from my childhood: this version gets its creamy texture from a potato and a dollop of greek yogurt. It is quick and easy to make and sure to warm the soul.
Melt the butter in a large Dutch oven or soup pot over medium-low heat. Add the onion, garlic, red pepper flakes, a pinch of salt and a few grinds of black pepper.
Stir to combine, then cover the pot and cook, stirring occasionally, until the onions have softened and are just starting to turn golden, about 8 to 10 minutes. Don’t brown the onions.
Meanwhile, trim bottoms off the broccoli then peel the stalks. Chop stalks into 1″–2″ pieces. Grab the broccoli tops and cut as closely to the base of the florets as you can. Slice any remaining stalks into chunks to match to the rest. Reserve the broccoli florets—you’ll use them later.
Add chopped broccoli stalks and potato to the pot and stir. Pour in 6 cups water and about 1 teaspoon salt. Raise the heat to high and bring the mixture to a boil, then reduce the heat to medium-low and cover the pot.
Simmer until the broccoli stalks and potatoes are tender throughout, about 20-25 minutes. Meanwhile, chop the reserved florets into small pieces.
Once the potato and stalks are tender, add halfof the florets to pot (you’ll add the other half after blending), stir, cover, and cook until they’re bright green, about 3 to 5 minutes. Remove the pot from the heat. Blend the soup with an immersion blender or a standing blender, working in batches. Return the puréed soup to the pot over medium heat.
Add the remaining florets. Cover the pot and cook until they’re bright green soft, another 5 to 7 minutes. Add all the Parmigiano Reggiano and about 4 oz (120 g) of cheddar; stir to combine. Set aside the remaining 50 g of cheddar for the crostini. Stir in the yogurt. Taste for seasonings and add more salt and pepper if desired.
Place the bread slices on a baking sheet and sprinkle with remaining cheese. Toast under the broiler of the oven until cheese is melted and bubbly. Cut into bite-sized crostini.
Divide the soup into bowls and top with a sprinkle of cheese, toasted crostini, and red pepper flakes, if desired. Leftover soup keeps well in the refrigerator for up to 4 days (though the color darkens a bit with time).